1. Field
The present disclosure relates to a nerve probe array, and more particularly, to a nerve electrode structure connected to a nerve to collect nerve signals through an electrode formed at a probe or apply an electrical stimulation to the nerve.
[Description about National Research and Development Support]
This study was supported by the High-Tech Convergence Technology Development program of Ministry of Science, ICT and Future Planning, Republic of Korea (Project No. 1711015332) under the superintendence of National Research Foundation of Korea.
2. Description of the Related Art
Recently, as a nerve interface used for neuroprosthetics or human-machine interface (HMI), a subminiature nerve electrode structure directly connected to a nerve to apply stimulation to the nerve or collect nerve signal information from the nerve has been studied.
As an example of the subminiature nerve electrode structure, a cuff electrode composed of a body having a broad area and made of a flexible material and an electrode embedded in the body is used.
In the cuff electrode, a flexible body is wound around the entire surface of a nerve like bandaging and is fixed thereto, and a nerve signal is detected through an electrode formed at the surface of the body.
However, the body of the cuff electrode is fixed to perfectly surround the outer circumference of the nerve bundle and thus press a part of the nerve bundle, which may disturb blood circulation in a blood vessel present at the nerve eqineurium and thus cause chronic pain. In addition, the body made of a polymer material does not allow oxygen, water or the like to pass therethrough, which may cause a pain or nerve necrosis at a portion where the body is applied. Therefore, long-term transplantation into the nerve is not easy.
Moreover, since the electrode collects nerve signals at a location out of the nerve bundle, a signal inside the nerve may not be properly read, and signals in the nerve fiber level may not be selectively obtained. Therefore, in case of the cuff electrode, the number of electrodes embedded is generally limited, which may be a factor for limiting applications of neuroprosthetics or HMI.
In order to supplement the problems of an extraneural electrode such as the cuff electrode, an intra-fascicular electrode in which an electrode body is directly inserted into a nerve may be used.
Representatively, there may be used a so-called transverse intra-fascicular multichannel electrode/longitudinal intra-fascicular electrode (TIME/LIFE) for inserting a thread-type electrode body into a nerve bundle to read a nerve signal, a Utah probe electrode having a plurality of probes arranged vertically at a plate-shaped body to put the probes into a corresponding nerve portion, a sieve electrode having a body having a thin plate shape, which may be inserted into a section of a partially cut nerve, so that the body has a hole through which a nerve bundle may pass and an electrode is arranged in the hole, or the like.
However, in case of the TIME/LIFE, it is not easy to position the electrode at a desired location in a nerve, and thus nerve selectivity is low. In addition, since the electrode may not be easily fixed after transplantation, the location of the electrode may be easily varied due to an external force, which is disadvantageous for long-term transplantation.
In case of the Utah electrode, many probes are inserted in a vertical direction of a nerve bundle with large intervals, which results in great redundant damage of neuron. In the fabrication process of the electrode, the material of the probe is limited to hard silicon, which may cause damage of neuron in the long term, and thus the nerve signal acquisition performance may deteriorate.
In addition, in case of the sieve electrode, due to excellent nerve selectivity, when a plurality of electrodes is embedded, a nerve signal corresponding to each electrode may be accurately mapped, but the nerve need to be cut, which results in very serious invasiveness to the nerve.